The present invention relates to a supported solid catalyst which is capable of presenting high catalytic activity and can be used for the polymerization of conjugated dienes, to the method of preparing it, and to its use for the preparation of polymers and copolymers of conjugated dienes.
The use of lanthanides as polymerization catalysts for conjugated dienes is well known to the person skilled in the art.
Various catalytic compositions having a base of rare earths have been described, in particular with rare-earth halides. Thus, Sci. Sin. 13(8):1339, 1964, describes the use of yttrium trichloride and Belgian Patent No. 644 291 describes the use of cerium trichloride. However, by reason of the very poor solubility of these salts in the aliphatic or aromatic hydrocarbon solvents used as polymerization solvent, these catalytic compositions had a heterogenous character and a poor catalytic activity, which greatly limited their use on an industrial scale.
Various solutions have been described in order to overcome this drawback. Thus, the use of binary catalytic systems resulting from the reaction of a trialkyl aluminum compound with a rare earth trihalide complexed by electron donors has been described. The use of alcohol is described in the "Journal of Polymer Science--Polymer Chemistry 19:3345, 1980" and the use of tetrahydrofuran has been described in "Macromolecules 15:230, 1982".
As another solution, "Kaustschuk und Gummi Kunstoffe 22:293, 1969" has described the use of ternary catalytic systems resulting from the reaction of a rare earth carboxylate, particularly of neodymium, with a halogenating agent and a trialkyl aluminum compound, the halogenating agent possibly being a halogenated derivative of alkyl aluminum.
It has furthermore been proposed to use quaternary catalytic systems, as in European Patent No. 7027, which describes a catalytic system coming from the reaction of the reaction product of a Lewis base and a carboxylate of a metal of the lanthanide series with an organic compound of aluminum, an alkyl aluminum halide, and a conjugated diene.
Finally, more recently, the "Journal of Macromolecular Science--Chemistry, A 26(2.sctn.3):p.405-416, 1989" has described catalytic systems formed of neodymium complexes supported on a copolymer of acrylic acid with an olefin in the presence of an organic compound of aluminum and an alkyl aluminum halide.